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ABSTRACT: We describe a fiber-optic gyroscope based on the Sagnac effect, realized on a multiplexed telecom fiber network. Our loop encloses an area of 20 km<sup>2</sup> and coexists with Internet data traffic. This Sagnac interferometer is capable of detecting signals that are larger than 10<sup>-8</sup> (rad/s)/Hz, thus approaching ring laser gyroscopes without using a narrow-linewidth laser or sophisticated optics. The proposed gyroscope could be useful for seismic applications, opening new possibilities for this kind of optical fiber sensor.
Optics Letters 04/2013; 38(7):1092-4. · 3.40 Impact Factor
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S. Schiller,
A. Görlitz,
A. Nevsky,
S. Alighanbari,
S. Vasilyev,
C. Abou-Jaoudeh,
G. Mura,
T. Franzen,
U. Sterr,
S. Falke, [......],
G. Barwood,
Y. Ovchinnikov,
J. Stuhler,
W. Kaenders,
C. Braxmaier,
R. Holzwarth,
A. Donati,
S. Lecomte, D. Calonico,
F. Levi
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ABSTRACT: The use of ultra-precise optical clocks in space ("master clocks") will allow
for a range of new applications in the fields of fundamental physics (tests of
Einstein's theory of General Relativity, time and frequency metrology by means
of the comparison of distant terrestrial clocks), geophysics (mapping of the
gravitational potential of Earth), and astronomy (providing local oscillators
for radio ranging and interferometry in space). Within the ELIPS-3 program of
ESA, the "Space Optical Clocks" (SOC) project aims to install and to operate an
optical lattice clock on the ISS towards the end of this decade, as a natural
follow-on to the ACES mission, improving its performance by at least one order
of magnitude. The payload is planned to include an optical lattice clock, as
well as a frequency comb, a microwave link, and an optical link for comparisons
of the ISS clock with ground clocks located in several countries and
continents. Undertaking a necessary step towards optical clocks in space, the
EU-FP7-SPACE-2010-1 project no. 263500 (SOC2) (2011-2015) aims at two
"engineering confidence", accurate transportable lattice optical clock
demonstrators having relative frequency instability below 1\times10^-15 at 1 s
integration time and relative inaccuracy below 5\times10^-17. This goal
performance is about 2 and 1 orders better in instability and inaccuracy,
respectively, than today's best transportable clocks. The devices will be based
on trapped neutral ytterbium and strontium atoms. One device will be a
breadboard. The two systems will be validated in laboratory environments and
their performance will be established by comparison with laboratory optical
clocks and primary frequency standards. In this paper we present the project
and the results achieved during the first year.
06/2012;
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ABSTRACT: In this paper we described the development and the characterization of a 578 nm laser source to be the clock laser for an Ytterbium Lattice Optical clock. Two indipendent laser sources have been realized and the characterization of the stability with a beat note technique is presented.
01/2011;
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F. Levi,
C. Calosso, D. Calonico,
L. Lorini,
E.K. Bertacco,
A. Godone,
G.A. Costanzo,
B. Mongino,
S.R. Jefferts,
T.P. Heavner,
E.A. Donley
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ABSTRACT: This paper describes the new twin laser-cooled Cs fountain primary frequency standards NIST-F2 and ITCsF2, and presents some of their design features. Most significant is a cryogenic microwave interrogation region which dramatically reduces the blackbody radiation shift. We also present a preliminary accuracy evaluation of IT-CsF2.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 04/2010; · 1.69 Impact Factor
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ABSTRACT: Caesium fountain frequency-standards realize the second in the International System of Units with a relative uncertainty approaching 10^-16. Among the main contributions to the accuracy budget, cold collisions play an important role because of the atomic density shift of the reference atomic transition. This paper describes an application of the Bayesian analysis of the clock frequency to estimate the density shift and describes how the Bayes theorem allows the a priori knowledge of the sign of the collisional coefficient to be rigourously embedded into the analysis. As an application, data from the INRIM caesium fountain are used and the Bayesian and orthodox analyses are compared. The Bayes theorem allows the orthodox uncertainty to be reduced by 28% and demonstrates to be an important tool in primary frequency-metrology. Comment: 13 pages, 5 figures, submitted to Metrologia, application of the Bayes theorem to metrology
07/2009;
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F. Levi,
C. Calosso, D. Calonico,
L. Lorini,
E.K. Bertacco,
A. Godone,
G.A. Costanzo,
B. Mongino,
S.R. Jefferts,
T.P. Heavner,
E.A. Donley
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ABSTRACT: This paper describes the new twin laser-cooled Cs fountain primary frequency standards NIST-F2 and IT-CsF2, and presents their most innovative design features. Most significant is a cryogenic microwave interrogation region which dramatically reduces the blackbody radiation shift. We present as well a preliminary accuracy evaluation of IT-CsF2.
Frequency Control Symposium, 2009 Joint with the 22nd European Frequency and Time forum. IEEE International; 05/2009
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ABSTRACT: In this paper the Bayesian analysis is applied to assign a probability density to the value of a quantity having a definite sign. This analysis is logically consistent with the results, positive or negative, of repeated measurements. Results are used to estimate the atom density shift in a caesium fountain clock. The comparison with the classical statistical analysis is also reported and the advantages of the Bayesian approach for the realization of the time unit are discussed. Comment: 10 pages, 4 figures, submitted to Metrologia
02/2009;
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ABSTRACT: The gravitational redshift is one of the main biases in the comparison of primary frequency standards; even if it is not a limit for the present accuracy of the microwave frequency standards such as Cs beam or fountain clocks, it could be a challenge for the forthcoming generation of atomic optical clocks. In this article we report the evaluation of the gravitational redshift with respect to the Geoid reference at Istituto Nazionale di Ricerca Metrologica (INRIM) laboratories, with an accuracy of 1 × 10−17 in terms of relative frequency. The evaluation is based on GPS/levelling measurements and on the use of both a local and a global model for the Earth Geoid; the main limitation to the accuracy is given by the Geoid reference potential itself.
Metrologia 09/2007; 44(5):L44. · 1.75 Impact Factor
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ABSTRACT: In this paper we present an accuracy evaluation of the primary frequency standard IEN-CsF1 of the Italian 'Istituto Nazionale di Ricerca Metrologica'. In particular, we discuss the major improvements applied to the frequency standard that have allowed us to reach a total uncertainty of 8 × 10−16 in a measurement period of 20 days to 25 days. The full metrological chain that links the IEN-CsF1 fountain to the International Atomic Time scale is described and characterized, with respect to its noise and performances.
Metrologia 11/2006; 43(6):545. · 1.75 Impact Factor
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A. Bauch,
J. Achkar,
S. Bize, D. Calonico,
R. Dach,
R. Hlavac,
L. Lorini,
T. Parker,
G. Petit,
D. Piester,
K. Szymaniec,
P. Uhrich
Metrologia 01/2006; 43:109-120. · 1.75 Impact Factor
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A Bauch,
J Achkar,
S Bize, D Calonico,
R Dach,
R Hlavać,
L Lorini,
T Parker,
G Petit,
D Piester,
K Szymaniec,
P Uhrich
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ABSTRACT: Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), National Institute of Standards and Technology (NIST), National Physical Laboratory (NPL), Laboratoire National de Métrologie et d'Essais—Observatoire de Paris/Systèmes de Référence Temps Espace (OP) and Physikalisch-Technische Bundesanstalt (PTB) operate cold-atom based primary frequency standards which are capable of realizing the SI second with a relative uncertainty of 1 × 10−15 or even below. These institutes performed an intense comparison campaign of selected frequency references maintained in their laboratories during about 25 days in October/November 2004. Active hydrogen maser reference standards served as frequency references for the institutes' fountain frequency standards. Three techniques of frequency (and time) comparisons were employed. Two-way satellite time and frequency transfer (TWSTFT) was performed in an intensified measurement schedule of 12 equally spaced measurements per day. The data of dual-frequency geodetic Global Positioning System (GPS) receivers were processed to yield an ionosphere-free linear combination of the code observations from both GPS frequencies, typically referred to as GPS TAI P3 analysis. Last but not least, the same GPS raw data were separately processed, allowing GPS carrier-phase (GPS CP) based frequency comparisons to be made. These showed the lowest relative frequency instability at short averaging times of all the methods. The instability was at the level of 1 part in 1015 at one-day averaging time using TWSTFT and GPS CP. The GPS TAI P3 analysis is capable of giving a similar quality of data after averaging over two days or longer. All techniques provided the same mean frequency difference between the standards involved within the 1σ measurement uncertainty of a few parts in 1016. The frequency differences between the three fountains of IEN (IEN-CsF1), NPL (NPL-CsF1) and OP (OP-FO2) were evaluated. Differences lower than the 1σ measurement uncertainty were observed between NPL and OP, whereas the IEN fountain deviated by about 2σ from the other two fountains.
Metrologia 12/2005; 43(1):109. · 1.75 Impact Factor
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ABSTRACT: This paper reports a review of the Blackbody Radiation (BBR) shift theory for the Cs atom hyperfine clock transition, together with a measurement of the Blackbody Radiation shift in an atomic cesium fountain.
Frequency and Time Forum, 2004. EFTF 2004. 18th European; 05/2004
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ABSTRACT: We report the theoretical evaluations of the static scalar polarizability of the 133Cs ground state and of the black body radiation shift induced on the transition frequency between the two hyperfine levels with m_F = 0. This shift is of fundamental importance in the evaluation of the accuracy of the primary frequency standards based on atomic fountains and employed in the realization of the SI second in the International Atomic Time (TAI) scale at the level of 1e-15. Our computed value for the polarizability is alpha_0=6.600(16)e-39 Cm^2/V in agreement at the level of 1e-3 with recent theoretical and experimental values. As regards the black body radiation shift we .nd for the relative hyper.ne transition frequency beta=-1.49 (7)e-14 at T = 300 K in agreement with frequency measurements reported by our group and by Bauch and Schroder [Phys. Rev. Lett. 78, 622, (1997)]. This value is lower by 2e-15 than that obtained with measurements based on the dc Stark shift and than the value commonly accepted up to now. Comment: 18 pages, 2 figures, 6 tables
10/2003;
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ABSTRACT: We used a Cs atomic fountain frequency standard to measure the Stark shift on the ground state hyperfine transiton frequency in cesium (9.2 GHz) due to the electric field generated by the blackbody radiation. The measures relative shift at 300 K is -1.43(11)e-14 and agrees with our theoretical evaluation -1.49(07)e-14. This value differs from the currently accepted one -1.69(04)e-14. The difference has a significant implication on the accuracy of frequency standards, in clocks comparison, and in a variety of high precision physics tests such as the time stability of fundamental constants. Comment: 4 pages, 2 figures, 2 tables
10/2003;
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ABSTRACT: In this paper we report the accuracy evaluation of the Italian primary frequency standard IEN-CsF1. We discuss the frequency shifts our frequency standard is corrected for and the procedure used for accuracy evaluation. In the last section we report a frequency comparison against two remote laboratory, the National Institute of Standard and Technology and the Physikalisch-Technische Bundesanstalt using the two way comparison technique.
Frequency control symposium and pda exhibition jointly with the 17th european frequency and time forum, 2003. proceedings of the 2003 ieee international; 06/2003
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F. Pereira Dos Santos,
H. Marion,
M. Abgrall,
S. Zhang,
Y. Sortais,
S. Bize,
I. Maksimovic, D. Calonico,
J. Grunert,
C. Mandache,
C. Vian,
P. Rosenbuch,
P. Lemonde,
G. Santarelli,
P. Laurent,
A. Clairon,
C. Salomon
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ABSTRACT: Over five years we have compared the hyperfine frequencies of <sup>133</sup>Cs and <sup>87</sup>Rb atoms in their electronic ground state using several laser cooled <sup>133</sup>Cs and <sup>87</sup>Rb atomic fountains with an accuracy of ∼10<sup>-15</sup>. These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies: d/dt In (νRb/νCs)=(0.2±7.0)×10<sup>-16</sup> yr<sup>-1</sup> (1σ uncertainty). The same limit applies to a possible variation of the quantity (μRb/μCs)α<sup>-0.44</sup>, which involves the ratio of nuclear magnetic moments and the fine structure constant. To improve this test, one needs more accurate cesium fountain clocks, for which the major limiting factor is the cold collision frequency shift. This effect can now be evaluated with great accuracy using a new method which we also present here. It is based on a transfer of population by adiabatic passage that allows to prepare cold atomic samples with a well defined ratio of atomic density and atom number. This method is used to perform a measurement of the cold collision frequency shift in a laser cooled cesium clock at the percent level. With improvements, the adiabatic passage would allow measurements of density-dependent phase shifts at the 10<sup>-3</sup> level in high precision experiments. With this precision, reaching an accuracy of 10<sup>-16</sup> is possible.
Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 2003. Proceedings of the 2003 IEEE International; 06/2003
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ABSTRACT: We report a preliminary systematic shift uncertainty evaluation of our cesium fountain and of the first comparison with the NIST-F1 clock of the National Institute of Standard and Technology (NIST) with a two way satellite comparison system. The stability of the time scale UTC (IEN), (generated with a commercial Cs beam) is insufficient to allow evaluation of systematic shifts by conventional techniques; therefore, the accuracy evaluation of the fountain was accomplished using mainly fast differential techniques, resulting in an overall uncertainty of 3×10<sup>-15</sup>.
IEEE Transactions on Instrumentation and Measurement 05/2003; · 1.21 Impact Factor
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H Marion,
F Pereira Dos Santos,
M Abgrall,
S Zhang,
Y Sortais,
S Bize,
I Maksimovic, D Calonico,
J Grünert,
C Mandache,
P Lemonde,
G Santarelli,
Ph Laurent,
A Clairon,
C Salomon
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ABSTRACT: Over five years, we have compared the hyperfine frequencies of 133Cs and 87Rb atoms in their electronic ground state using several laser-cooled 133Cs and 87Rb atomic fountains with an accuracy of approximately 10(-15). These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies: d/dt ln([(nu(Rb))/(nu(Cs))]=(0.2+/-7.0)x 10(-16) yr(-1) (1sigma uncertainty). The same limit applies to a possible variation of the quantity (mu(Rb)/mu(Cs))alpha(-0.44), which involves the ratio of nuclear magnetic moments and the fine structure constant.
Physical Review Letters 05/2003; 90(15):150801. · 7.37 Impact Factor
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ABSTRACT: At BNM-SYRTE laboratories in Paris two 133Cs fountains and a 87Rb one have been already demonstrated. This paper illustrates the construction of a 87Rb and Cs dual fountain realized within the same structure to work simultaneously. Up to now only the Cs part is under operation but Rb part, already completed, will be soon operational. The experiment has been projected to improve present fountain frequency standards and to perform a more precise laboratory test (at 10E-16 level) on a possible time variation of the fine structure constant alpha, as recent cosmological evidences strongly motivates.
01/2003;
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ABSTRACT: We report the first accuracy evaluation of the new IEN Cs fountain primary frequency standard. Although preliminary, and performed in absence of a resident H-maser, all the principal effects are evaluated at few units of 10<sup>-15</sup> level. Differential measurements and TWSTFT remote comparisons were used to supply in the absence of the H-maser.
Precision Electromagnetic Measurements, 2002. Conference Digest 2002 Conference on; 02/2002
